This application requests support to examine the prevalence of hypertension and associated risk factors in black populations in the U.S., West Africa and the Caribbean. Blacks experience twice the rates of hypertension as whites in the U.S., for reasons which remain incompletely understood. Research in the epidemiology of hypertension has successfully identified a number of environmental risk factors; a systematic study of the impact of these risk factors on hypertension rates in blacks should yield new insight into this disease process. An international collaborative study comparing black populations in Africa and the Western Hemisphere offers the opportunity to separate the impact of genetic and environmental factors. Based on a standardized common protocol, data will be collected on the following variables: blood pressure (BP), age, sex, height, weight, waist/hip ratio, urinary sodium/potassium excretion, alcohol and calcium intake, and assessment of social status/incongruity. The samples will be drawn from Chicago, IL, St. Lucia, the West Indies, and from both urban and rural communities in Nigeria and the Republic of Cameroon (N = 6 sites). A total of 1600 individuals, in the age range 25-64, will be enrolled at each site. Study coordination, including training of survey teams and data processing and analysis, will take place in Chicago. The principal aims of this study are: (1) To determine the direction and magnitude of the relationship between the risk factors and BP, in each population separately, (2) To estimate group differences in the risk factors, (3) To estimate the proportion of excess hypertension risk in the U.S. sample that can be accounted for by the measured variables, and (4) To estimate prevalence rates of hypertension in these geographically dispersed populations which share a common West African genetic heritage. Excess risk associated with hypertension accounts for as much as 10% of the black:white differential in adult mortality. The findings in this study will provide direct evidence regarding the evolution of the high rates of hypertension experienced by U.S. blacks, and offer insight into the key environmental exposures which cause this common disease. These data will greatly strengthen public health programs aimed at prevention and control of hypertension.